This invention relates to a new and improved densitometer which employs a solid-state image sensor as the detector.
The densitometer is an instrument used for quantitative measurement of a sample, such as a spot developed and separated on a support in thin-layer chromatography, which is commonly referred to as TLC. For measurement the sample spot is illuminated, and the light reflected by or transmitted through the spot is detected by a detector to produce a corresponding electrical signal, from which the density and consequently the quantity of the sample can be calculated.
Sample spots developed on a TLC plate differ in shape, thickness and size, and the distribution of the density of the sample components is not always uniform in each spot. In order to reduce error or inaccuracy in measurement caused by the nonuniformity of the density distribution in the spot it has been proposed to scan the whole area of the spot in a zigzag way by a thin light beam having a small cross section as compared with the area of the spot.
The method, however, requires a long time for measurement and a complicated mechanism for scanning, with a relatively low signal-to-noise ratio caused by the small cross section of the scanning light beam.
In recent years the solid-state image sensor which comprises an array of photodiodes has been developed and come to be used in densitometers as the detector. In the conventional densitometers, however, a photodiode array is arranged on the plane where the image of a sample is formed by the light that has passed a filter, which can provide only one wavelength.
Accordingly, the primary object of the invention is to provide a densitometer which uses a single or a plurality of image sensors as the detector in combination with a monochromator in such a manner as to enable free selection of wavelength.
Another object of the invention is to provide such a densitometer as aforesaid which makes it easy to perform dual-wavelength measurement.
Another object of the invention is to provide such a densitometer as aforesaid which is capable of measuring the density of a sample quickly and with a high degree of accuracy and precision.
Another object of the invention is to provide such a densitometer as aforesaid which is simple in structure, compact in size and low in manufacturing and maintenance cost.
Another object of the invention is to provide such a densitometer as aforesaid in which an electronic computer provides the measurement data in various desired forms.